As demands for application of Internet of Things (IoT) in next generation mobile communication networks become wider and wider, a new wireless communication technology is under study in the 3rd Generation Partnership Project (3GPP), namely, a subject on Narrowband Internet of Things (NB-IoT) technology, so as to support IoT traffics.
The IoT traffics have many new features, including extra-low power consumption requirement, deployment of massive user equipments, relatively few data traffic, and low requirement on traffic latency, etc. Such features place many technical requirements on a long-term evolution (LTE) system, an important requirement in which is the extra-low power consumption requirement on the user equipment.
The NB-IoT technology is a new narrowband communication technology that is further enhanced and based on existing LTE technologies. In uplink data transmission of the NB-IoT, a media access control (MAC) layer uses asynchronous transmission, and feedback information of its uplink transmission is indicated by scheduling information of a physical downlink control channel (PDCCH).
For example, if a user equipment (UE) receives a PDCCH scheduling new data after transmitting uplink data, it shows that transmission of the uplink data is successful. And if the UE receives a PDCCH scheduling retransmission, it shows that the transmission of the uplink data fails, and retransmission of the MAC layer needs to be performed. For a UE configured with discontinuous reception (DRX), a drx-inactivityTimer shall be started after the PDCCH scheduling new data is received. The UE enters into a DRX status only when the drx-inactivityTimer expires or a discontinuous reception command (DRX command) from a network side is received, so as to lower power consumption.
On the other hand, in the transmission of uplink data of the NB-IoT, a radio link control (RLC) layer of the UE determines whether the uplink data have been successfully received via a status report (SR) fed back by a receiving device. A transmitting device only carries a poll bit in a last uplink datum, so as to show that the datum is the last datum. And after receiving the last uplink datum, the receiving device will indicate to the transmitting device in a form of an RLC status report that the uplink data have been successfully received, or indicate lost data.
It should be noted that the above description of the background is merely provided for clear and complete explanation of this disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of this disclosure.